Network module

ABSTRACT

A home network, in one embodiment including a home wiring system; a demarcation point unit in electrical communication with the home wiring system; and a home network module in electrical communication with the home wiring system. The home network module is adapted for connection to a home electronic device. The demarcation point unit passes data to and receives data from the home electronic device through the home network module.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/022,272, filed Jan. 30, 2008, entitled “Home Network System andMethod,” now issued as U.S. Pat. No. 8,724,485, which is a divisionalapplication of U.S. patent application Ser. No. 09/943,424 filed on Aug.30, 2001 entitled “Home Network System and Method,” now issued as U.S.Pat. No. 8,761,200, both of which are hereby incorporated by referencein their entireties for all purposes. The Ser. No. 09/943,424application claims the benefit of the filing date of U.S. ProvisionalApplication, Ser. No. 60/229,263, filed Aug. 30, 2000, entitled “HomeNetwork Method And Apparatus,” and Provisional Application, Ser. No.60/230,110, filed Sep. 5, 2000, entitled “Home Network Method AndApparatus,” the entirety of which provisional applications isincorporated by reference herein. The Ser. No. 09/943,424 applicationfurther claims the benefit of the filing date of U.S. ProvisionalApplication, Ser. No. 60/275,060, filed Mar. 12, 2001, entitled “HomeNetwork Uses Frequencies Above CaTV,” and Provisional Application, Ser.No. 60/291,130, filed May 15, 2001, entitled “Home Network Method AndApparatus,” and Provisional Application, Ser. No. 60/297,304, filed Jun.11, 2001, entitled “Home Network Uses Frequencies Above CaTV,” all ofwhich are hereby incorporated by reference in their entireties for allpurposes.

FIELD OF THE INVENTION

The invention relates to communication networks in general and morespecifically to networks suitable for use in residential buildings.

BACKGROUND OF THE INVENTION

As the number of electronic devices in the home has increased there hasbeen a demand for a way to permit those devices to communicate betweenthemselves and with external networks. Several standards are evolvingprotocols that will permit devices to communicate over twisted pair andother wiring modalities.

However, a large number of homes are presently equipped with coaxialcable to permit the viewing of cable television programming or to permitconnection of computer devices to the internet. The evolving standardsdo not appear to take into account this installed base of coaxial cable.Instead, such standards require the rewiring of homes, in order tocomply with the evolving protocol, or the use of other existing media,such as power lines, telephone lines, or wireless links. In comparisonto coaxial cables, however, such existing media supports a significantlylower bit rate.

This invention meets this demand for interconnectivity without thenecessity of changing the physical wiring present in the home.

SUMMARY OF THE INVENTION

The invention relates to a home network. In one aspect, the inventionfeatures a home network including a network backbone, a plurality ofmodules connected to the network backbone, and a demarcation point unit.Each module is connected between the network backbone and a local bus.The demarcation point unit receives a home network signal from one to ofthe modules over the network backbone and returns the home networksignal to the plurality of modules. The network backbone includes aplurality of coaxial cables and, in one embodiment, a splitter.

A module is in communication with a plurality of local buses.Embodiments of the local bus include a 1394 local bus, a universalserial bus (USB), Ethernet bus, Internet protocol (IP) bus. In oneembodiment, at east two of the modules are in communication with 1394local bus.

The demarcation point unit is in communication with an external networkand receives a cable TV (CaTV) signal from the external network. TheCaTV and the home network signals pass together over the networkbackbone to the modules. In one embodiment, the frequency of the homenetwork signal is approximately in the 960-1046 MHz frequency range. Adevice in communication with the demarcation point unit can receive theCaTV signal directly without passing through a module.

The demarcation point unit includes a signal reflector unit. In oneembodiment, the signal reflector unit that receives the home networksignal from one module—the home network signal is at a first frequency.The signal reflector unit returns the home network signal to theplurality of modules of the home network signal having a secondfrequency. The first frequency can be the same as or different (e.g.,higher or lower) than the second frequency.

In another aspect, the invention features a home network including ademarcation point unit and a plurality of modules. The demarcation pointunit receives a signal from a network that is external to the home. Eachof plurality of modules is connected to the demarcation point unit byone or more coax cables and to a device by a local bus. One of themodules receives a message from the device connected to that one moduleby the corresponding local bus and transmits the message to thedemarcation point unit. The demarcation point unit receives the messagefrom that one module and transmits the message and the signal togetherto each of the plurality of modules over the coax cables.

In yet another aspect, the invention features a demarcation point unitthat connects a home network and an external network. The demarcationpoint unit includes a diplexer that receives a first signal from thehome network and a second signal from the external network. The diplexerseparates the first signal from the second signal. A signal reflectorunit receives the separated first signal from the diplexer and returnsthe first signal to the diplexer for transmission to the home network.

In one embodiment, the signal reflector unit includes a coax cable thatreflects the first signal received from the diplexer back to thediplexer. The coax cable of the signal reflector unit can be shorted toground or unterminated. In another embodiment, the signal reflector unitincludes a delay line in communication with the diplexer. The other endof the delay is shorted to ground or unterminated.

The signal converter unit in another embodiment includes a RF converterthat changes a frequency of the first signal before the first signalreturns to the diplexer. The signal passing to the diplexer from thehome network is an upstream signal. The signal returning to the diplexerfrom the signal reflector unit is a downstream signal. The signalreflector unit includes a second diplexer having an input/output (I/O)in communication with a first diplexer and an input in communicationwith the RF converter. The second diplexer separates the upstream signalreceived by the I/O from the downstream signal received by the input.The second diplexer returns the downstream signal to the first diplexerover the I/O.

An output in communication with the RF converter passes the upstreamsignal to the RF converter over the output. The RF converter includes aRF down-converter in communication with a RF up-converter. The RPdown-converter changes the frequency of the upstream signal to anintermediate frequency. The RF up-converter changes the intermediatefrequency to the frequency of the downstream signal. In one embodiment,the frequency of the upstream signal is higher than the frequency of thefirst signal. Also, the power level of the upstream signal received atthe signal reflector unit is constant, and the power level of thedownstream signal leaving the signal reflector unit is also constant.

In the signal reflector, a splitter can be connected between thediplexer and the home network. The splitter receives the downstreamsignal from the diplexer and transmits the returned downstream signal tothe home network over a plurality of coax cables. The splitter receivesthe upstream signal from the home network for transmission to thediplexer. The diplexer combines the first signal received from thesignal reflector unit with the signal received from the external networkand transmits the combined signal to the home network.

In another aspect, the invention features a network module that connectsa network backbone to a local bus. The network module includes adiplexer that receives an analog signal and separates a home networksignal from the analog signal. A modem converts the home network signalto a digital signal. A media access controller (MAC) interfaces with aprotocol of the local bus to deliver the digital signal to the localbus.

In another aspect, the invention features a method for use by modules ina home network for communicating with each other over a coax backbone. Acycle start burst is transmitted over the backbone to start atransmission cycle during which the network modules transmit bursts overthe backbone. A first portion of the transmission cycle is allocated forthe transmission of isochronous bursts by the network modules. A secondportion of the transmission cycle is allocated for the transmission ofasynchronous bursts by the network modules.

A transmission order is established for the network modules to followwhen transmitting isochronous and asynchronous bursts over the backbone.The cycle start burst includes the transmission order. Isochronousbursts start at the start of every transmission cycle, followed by thetransmission of asynchronous bursts. Transmission of an asynchronousburst is allowed to complete after the end of the transmission cycle.

In one embodiment, those network modules that are requesting bandwidthfor transmitting isochronous bursts are determined. One of the modulesis designated to be a master network module, which transmits the cyclestart burst. The network modules synchronize to the cycle start burst.

In another embodiment, bandwidth is allocated in the first portion ofthe transmission cycle to each network module requesting a guaranteedquality of service. Asynchronous bursts are monitored, by a givennetwork module, on the backbone to determine when a given network modulecan transmit an asynchronous burst. The given network module receives agrant over the backbone to indicate that the given network module cantransmit an asynchronous burst.

In another embodiment, isochronous bursts are monitored by a givennetwork module on the backbone to determine when that network module cantransmit an isochronous burst. An empty burst is transmitted by a givennetwork module if the given network module has no data to transmitduring the second portion of the transmission cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is pointed out with particularity in the claims. Thedrawings are not necessarily to scale, emphasis instead generally beingplaced upon illustrating the principles of the invention. Like referencecharacters in the respective drawing figures indicate correspondingparts. The advantages of the invention described above, as well asfurther advantages of the invention, may be better understood byreference to the description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a block diagram of an embodiment of a home network systemconstructed in accordance with the invention;

FIG. 2 is a block diagram of an embodiment of a demarcation point unitincluding a home network reflector unit as shown in FIG. 1;

FIG. 2A is a block diagram of another embodiment of the home networkreflector unit;

FIG. 3 is a block diagram of an embodiment of a home network module;

FIG. 4 is a block diagram of an embodiment of a physical layer of thehome network module of FIG. 3;

FIG. 5 is a block diagram of embodiments of a modem in the home networkmodule of FIG. 3;

FIG. 6 is a diagram of an embodiment of a burst or message;

FIGS. 7A-7C illustrate a timing diagram showing an exemplary sequence ofcommunication cycles on a backbone of the home network;

FIGS. 8A-8B are flow diagrams illustrating an embodiment of a process bywhich the master home network module controls communication on the coaxbackbone;

FIG. 9 is a flow diagram illustrating an embodiment of a process bywhich each home network module in the home network, other than themaster home network module, communicates over the backbone of the homenetwork;

FIG. 10 is a flow diagram illustrating an embodiment of a process bywhich a new home network module registers to become part of homenetwork;

FIG. 11 is a logical diagram of the home network, in which the backboneconnects four IEEE 1394 local buses through different home networkmodules;

FIG. 12 is a conceptual diagram of an emulated bus structure from theperspective of each home network module;

FIG. 13 is a flow diagram illustrating a process performed by each ofthe home network modules to initialize a 1394 bus in the home network;

FIG. 14 is a flow diagram illustrating an embodiment of a process bywhich each home network module handles 1394 asynchronous packetsreceived from the backbone in an emulated bus embodiment;

FIG. 15 is a flow diagram illustrating an embodiment of a process bywhich each home network module handles 1394 asynchronous packetsreceived from a 1394 local bus in an emulated bus embodiment; and

FIG. 16 is a block diagram of another embodiment of the demarcationpoint unit.

DETAILED DESCRIPTION

In brief overview, FIG. 1 shows an embodiment of a home network 10,constructed in accordance with the invention, including a demarcationpoint unit (DPU) 14 located at the entry point into a home, whichoperates as the interface between the home network 10 and an externalnetwork 18, such as a cable television (TV) network or the Internet. TheDPU 14 is in communication with a plurality of home-network modules(HNM) 28, 28′, 28″, 28′″ (generally 28), each located in one of variousrooms of the home. Each HNM 28 is the interface between devices in aroom (e.g., home entertainment devices and computer devices) and the DPU14.

Implementing the home network 10 in the home does not require therewiring of the cable TV equipment that is typically already installedin many homes for accessing the cable TV network 18 or the Internet. TheHNMs 28 communicate with the DPU 14 and with each other over standardcable equipment. Such cable equipment includes coaxial (or coax) cables22, splitters (generally 24), and cable TV outlets 26. This installedcable equipment operates as a backbone of the home network 10 forconveying inter-room communications. Although the home network 10 canoperate with existing coax wiring, the principles of the invention applyalso to other types of wiring, such as CAT-5 or plastic fiber. Ingeneral, the home network 10 operates in parallel to the cable TVservices, leaving legacy cable TV signals and devices (such as set topboxes and cable modems) unaffected.

With this existing coax cable equipment, the home network 10 joinsvarious computer devices, such as personal computers and peripherals(printer, scanner, CD etc.), and entertainment equipment, such as settop boxes (STB), televisions, videocassette recorders, personal videorecorder (PVR), etc., located throughout the home into one network. Bythis one network, various computer devices in different rooms can shareaccess to the Internet, and video or audio sources played in one roomcan be enjoyed in another room of the home. In one embodiment, describedin more detail below, the existing cable equipment provides aninter-room backbone for an IEEE-1394 (FireWire) network.

More specifically, in an exemplary embodiment of the home network 10,HNMs 28, 28′, 28″, 28′″ in respective rooms 30, 30′, 30″, 30′″(generally 30) are connected to the home network backbone through cableTV outlets 26. The home network backbone (referred to hereafter asbackbone 20), includes a plurality of coax cables 22 that connect thecable TV outlets 26, and thus the HNMs 28, to the DPU 14. The coaxcables 22 connect to the splitters 24, which distribute the signalsreceived from the external network 18 and from the HNMs 28 to each ofthe rooms 30 connected to the home network 10. In the embodiment shownin FIG. 1, the DPU 14 includes one of the splitters 24′; in anotherembodiment, instead of being part of the DPU 14, that splitter 24′ isconnected to an output of the DPU 14. In some embodiments, a residentialgateway device is located at the demarcation point (i.e., the entrypoint of the coax cable to the home) to exchange signals between theexternal network 18 and other devices in the house, such as a cablemodem or a STB. Embodiments of the residential gateway provide Internetaccess (e.g., cable modem, digital subscriber line (DSL)). Otherembodiments provide the functionality of a set top box, of a personalvideo recorder, or of a tuner for multiprogramming. In each of theseembodiments, the DPU 14 can be integrated into or be external to suchthe residential gateway device.

Each room 30 includes one or more devices 33. Devices 33 include, forexample, digital video disc (DVD) players, videocassette recorders(VCR), game consoles, interactive televisions computers, scanners, faxmachines, printers, analog televisions, digital televisions, set topboxes, stereo systems, and camcorders. In each room 30 having a device33 that the resident of the home wants to make available for inter-roomcommunication, there is located a HNM 28 that connects that device 33 tothe backbone 20. For example, rooms 30, 30′, 30″, and 30′″ each havedevices 33 that the resident chooses to have inter-room communicationcapability; so, in each of these rooms an HNM 28 connects those devices33 to the backbone 20.

Devices 33 within a given room 30 that communicate according to the sameprotocol (e.g., USE (universal serial bus), IP (Internet Protocol),Ethernet, and IEEE-1394) are typically connected to the same local bus35. Each HNM 28 can interface with one or more different types of localbuses (generally 35). For example, in room 30 the HNM 28 interfaces witha local 1394-bus 35′, connected to an analog set-top box and a DVDplayer, and a local data-bus 35″ (e.g., Ethernet, USB, IP), connected toanalog set-top box and a personal computer. In one embodiment, devices33 in different rooms of the same local bus type (e.g., 1394) cancommunicate with each other over the backbone 20, whereas devices 33 ofdifferent local bus types (e.g., 1394 and USB) do not. In someembodiments, the HNM 28 resides in the entertainment or data device, inother embodiments, the HNM 28 resides in a separate box.

In addition to the various types of local buses 35, the HNM 28 canconnect to other devices 33 in the room 30 by coax cable. For example,the HNM 28 in room 30 also connects to the analog set-top box by coaxcable 36. Although shown in FIG. 1 to be separate from the analogset-top box, in one embodiment the HNM 28 is a built-in component of theset-top box.

Each HNM 28 communicates with the DPU 14 and each other HNM 28 on thebackbone 20 with analog signals and converts analog signals receivedfrom the DPU 14 and the HNMs 28 into digital signals for delivery todevices 33 connected to that HNM 28. If a room 30 has a legacy device 33requiring an analog signal (such as an analog or digital TV), but doesnot have a set-top box, an interface box can convert the digital signalproduced by the HNM 28 into a signal that is appropriate for that legacydevice. For example, in room 30′, the HNM 28′ communicates with theanalog TV, which requires an analog signal, through the interface box32, which converts 1394 digital signals to audio/visual analog signals.

Instead of being on the same local bus 35, devices 33 of the sameprotocol within a given room 30 can connect to the same HNM 28 bydifferent local buses 35. With this arrangement, such devices 33 cancommunicate with devices 33 in other rooms 30 of the home.

Devices 33 that the resident does not want to participate in inter-roomcommunication can connect directly to the external network 18 withoutthe use of the HNM 28. For example, in room 30 ^(iv), the analogtelevision set is connected directly to the backbone 20 without anintervening HNM 28. Such devices 33 continue to receive the legacy cableTV signals from the cable TV network or have broadband access to theInternet through the DPU 14.

In operation, each HNM 28 permits those devices 33 connected to that HNM28 to communicate with other devices 33 in different rooms 30, toreceive programming from the cable television, and to have broadbandaccess to the Internet (e.g., through a cable modem, DSL service, andSatellite). For example, a DVD disc playing in the DVD player in room 30can be viewed on the digital television in room 30″ and that digitaltelevision can also receive programming from the cable televisionnetwork 18. Similarly, computer devices in various rooms can communicatewith one another using their respective HNMs 28 connected to thebackbone 20. For example, the personal computer (PC) in room 30 canprint a document on the printer or share a file with the personalcomputer in room 30′″, or access the Internet through a cable modem (orDSL or audio modem). In accordance with the principles of the invention,the analog signal to and from the Internet (or cable provider) runs overthe same coax wires 22 in the house and at the same time as theinter-room communication signals (hereafter the home network signal). Ineach case, the signal received from the cable television network orInternet provider are routed to the proper electronic devices by way ofthe DPU 14 and the appropriate HNM 28.

FIG. 2 shows an embodiment of the DPU 14 including a diplexer 40, ahome-network reflector unit (HRU) 44 and a splitter 24″. In general, thediplexer 40 separates a cable TV (CaTV) signal (or satellite signal)received from the external network 18 from a home network signalreceived from the HNMs 28 connected to the backbone 20. One input/output(I/O) port (the “L” port) of the diplexer 40 transmits and receives theCaTV signal (or satellite signal) to and from the external network 18.Another I/O port (the “H” port) of the diplexer 40 transmits andreceives the home network signal to and from HRU 44. The diplexer 40also combines the CaTV (or satellite) signal received from the externalnetwork 18 with the home network signal received from the HRU 44 andpasses the combined signal to the splitter 24′ through a third I/O portfor subsequent transmission to the HNMs 28 over the backbone 20.

The “L” port uses a low-pass filter at a certain predeterminedfrequency, fc, and the “H” port uses a high-pass filter at the samefrequency, fc. By setting the frequency, fc, to about 900 MHz, forexample, the low-pass “L” port transfers TV signals (5-860 Mhz), and thehigh-pass “H” port transfers the home network signal above 860 MHz. Morespecifically, one embodiment sets the cutoff frequency to 950 MHz toseparate frequencies above 950 MHz for use by the home network signalfrom the CaTV signals, which are in the 5-860 MHz range.

If satellite TV signals are used inside the home, the frequency, fc, isset to about 2100 MHz, to separate the satellite TV signals (950-2100MHz) from the home network signal (below 950 MHz or above 2100 MHz). Inthis satellite example, the “L” port is connected to the externalnetwork 18 and the “H” port is connected to the HRU 44. Alternatively,the cutoff frequency, fc, is set to about or below 900 MHz, and the homenetwork signal uses frequencies below the satellite TV signals. In thissatellite example, the “H” port is connected to the external network 18and the “L” port is connected to the HRU 44.

In some embodiments, the HRU 44 is either an unterminated or a shortedcoaxial cable, which reflects the home network signal received from thediplexer 40 back to the diplexer 40. Some embodiments of a passive HRUconnect one port of a passive delay line to the H port of the diplexer40 to improve the performance of the network 10 by avoiding signalfading. In such embodiments, the other port of the passive delay line isunterminated or shorted. In still other embodiments, leaving an outputof the diplexer 40 unterminated or by shorting that output to groundattains reflection of the home network signal. These embodiments of theHRU 44 are referred to as passive HRUs.

FIG. 2A shows another embodiment of the HRU 44 including a diplexer 42,band pass (BP) filters 46, 48, amplifiers 50, 52, an RF down-converter54, an RF up-converter 56 and an intermediate frequency filter andamplifier unit 58. The diplexer 42 along with the BP filters 46, 48separate the upstream signal from the downstream signal. The upstreamsignal is the signal coming from the backbone 20 to the HRU 44, anddownstream signal is the signal returning from the HRU 44 to thebackbone 20. The upstream signal coming from a transmitting HNM 28enters the diplexer 40 and passes to the internal diplexer 42 of the HRU44. The signal from the diplexer 42 is band pass filtered by BP filter46, amplified by amplifier 50, and RF down-converted by down-converter54 to an intermediate frequency (IF). In one embodiment, theintermediate frequency is 630 MHz. Other different frequencies can beused without departing from the principles of the invention. Usage ofthe intermediate frequency simplifies the RF design, by keeping thesignal, its images, and the local oscillator frequency separate fromeach other. Having the BPFs 46, 48 external to the diplexer 42simplifies the implementation of the diplexer 42.

The IF filter and amplifier unit 58 then amplifies and band pass filtersthe IF signal. The RF up-converter 56 shifts the frequency of the IFsignal up to the downstream frequency band. The amplifier 52 and BPfilter 48 then amplify and filter the downstream signal. The amplifiers50, 52 with the amplification provided by the IF filter and amplifierunit 58, sufficiently amplify the home network signal to improve thereach of the home network signal inside the home. This downstream signalthen passes through the diplexers 42, 40 back to the backbone 20 of thehome network 10. Thus, the HNMs 28 communicate with each other byissuing messages to the backbone 20 (i.e., the upstream signal). The HRU44 receives the upstream signal, amplifies and shifts the RF frequencyof the upstream signal, and then returns the upstream signal with theshifted frequency to the backbone 20 as the downstream signal. The HNMs28 then receive the messages in the downstream signal from the backbone20. Before the downstream signal reaches the backbone 20, the diplexer40 combines the downstream signal with the CaTV signal (or satellite)for transmission over the in home coax wires 22.

The home network 10 employs transmission power control. Each HNM 28adjusts its transmission power to such a power level that when itstransmitted signal arrives at the HRU 44, that signal has a predefinedpower level. Thus, the input power of the upstream signal arriving atthe HRU 44 remains constant because each HNM 28 uses an appropriatetransmission power level to account for the attenuation of the signalover the backbone 20 and thereby achieves the predefined power level atthe HRU 44. Also because power level of the inputted upstream signal isconstant and the amplification performed by the HRU 44 is constant, thedownstream signal leaving the HRU 44 is also constant.

In one embodiment, the upstream signal at the input to the HRU 44 is −50dBm, and the downstream signal at its output is −10 dBm. Accordingly, aHNM 28 can transmit at a power between −10 dBm, if located far from theHRU 44, and −50 dBm if located close to the HRU 44. The actualtransmitted power is determined according to the attenuation between theremote HNM 28 and the HRU 44. For instance, if the attenuation is 10 dB,the HNM 28 should transmit −40 dBm. If the HNM 28 is located 40 dB fromthe HRU 44, that HNM 28 should transmit at a power of −10 dBm so thatthe upstream signal can reach the HRU 44 with a power of −50 dBm.

The HRU 44 transmits at a constant power (e.g., −10 dBm). Therefore, ifthe HNM 28 is located 25 dB from the HRU 44, that HNM 28 receives thedownstream signal at a power of −35 dBm (−10 dBm−25 dBm=−35 dBm),irrespective of which HNM 28 sent the upstream signal to the HRU 44 thatreflected back as the downstream signal.

Employing this transmission power control simplifies significantly thegain control function at the receiver and at the transmitter of the homenetwork signal, particularly if each HNM 28 can set the gain just onceduring initialization.

In one embodiment, the home network signal transmitted over the homenetwork backbone 20 is in the 960 to 1046 MHz frequency range, but otherfrequency bands above the CaTV signals can be used. The CaTV signal(including the signal from Internet providers) is in the frequency rangeof 5 to 860 MHz. Table 1 shows that frequencies above 960 MHz areavailable for use in those homes in which CaTV signals are installed. Itshould be noted that at frequencies greater than 1000 MHz, low qualitysplitters found in the home provide poor signal isolation and returnloss performance.

TABLE 1 Frequency Range (MHz) Signal 870-896 Cellular mobile phoneuplink 896-902 Private land mobile radio 902-928 Amateur radio servicereserve 928-932 Domestic public radio service (paging) 944-947 Broadcastradio service (intercity relay) 950-2100 DBS (Satellite over coax)

In another embodiment, the home network signal is in the 5-45 MHzfrequency range. This frequency band is used by the U.S. cabletelevision operators for reverse path signals, i.e., signals that thehome devices 33, such as set top boxes (STB) and cable modems (CM),transmit back to the cable provider (i.e., the head-end). For theEuropean standard (called DVB), the reverse path frequency is located inthe band from 5-65 MHz.

Reverse channel signals transmitted to the head-end include the ReverseData Channel Out Of Band (RDC OOB) signals from the STB and the ReverseData Channel of the CM (RDC CM). To ensure proper operation of theset-top boxes and cable modems over the home network 10, the reversechannel signals should return seamlessly to the head-end. The head-enddetermines the actual frequencies used for the reverse channel signalsand the bandwidth for each channel is small compared to the 5-45 MHzfrequency range. Typically, but not necessarily, the set-top boxes andcable modems in the home use the same programmable frequencies for thereturn channel. The head-end determines the frequency allocation andtransmits information regarding the allocated frequencies to the devices33 in the home.

To transmit this information, the head-end uses frequencies above 50MHz. This communications channel, at frequencies above 50 MHz, is termedthe Out of Band Forward Data Channel (OOB FDC). Because frequenciesabove 50 MHz pass freely through the home network 10, this OOB FDCsignal carrying RDC OOB and RDC CM information passes unimpeded to theset top boxes and the cable modems connected directly (that is notthrough a HNM 28) to the coaxial cable 22.

FIG. 3 shows an exemplary conceptual embodiment of an implementation ofthe HNM 28, which functions as bridge between the coax backbone 20 andeach local bus 35. In brief overview, the HNM 28 receives a signal froma device 33 through a data port and converts that signal into amodulated analog signal over the backbone 20, combined with the Cable TVsignal. In the other direction, the HNM 28 receives an analog signalover the backbone 20 and converts the analog signal into a data signal.In one embodiment, the HNM 28 is implemented as an IC (integratedcircuit) chip set that is incorporated in an entertainment or datadevice, or in a standalone box.

The backbone-side of the HNM 28 includes a physical layer 90, a mediaaccess control (MAC) layer 92, and a network layer 94. The MAC layer 92supports constant bit rate (CBR) transmission and an unspecified bitrate (UBR) transmission with CBR 96 and UBR 98 protocols, respectively.To support quality of service (QoS) requirements, the CBR protocol 96 isused for the transmission of isochronous data and the UBR protocol 98for the transmission of asynchronous data. The network layer 94 includesa switching fabric 100 for controlling the flow of isochronous andasynchronous traffic between the backbone 20 and each local bus 35.

The architecture of the protocol stack on the local-bus-side of the HNM28 depends on the type of local bus. For example, if the local bus is anIEEE 1394 bus, then the HNM 28 includes a 1394 Phy layer 102, a 1394.1link layer 104 (with bridge functionality), and a network layer 106 thatsupports isochronous 107 and asynchronous 108 transmissions. In oneembodiment, the local bus is an Ethernet bus, which hasEthernet-specific Phy and MAC layers. In another embodiment, the localbus is a universal serial bus (USB), which correspondingly hasUSB-specific Phy and data link layers. In an embodiment in which the HNM28 is integrated in a device, such as a set top box and a personalcomputer, the bus is specific and internal to that device, and thebus-side of the protocol stack includes a device-specific interface forcommunicating on the bus.

In other embodiments, the HNM 28 operates as a bridge between thebackbone 20 and a plurality of local buses of different types. Forexample, as shown in FIG. 3, the HNM 28 is a bridge for 1394, 802.3, anda USB local buses. The HNM 28 can support other types of local buses anddifferent combinations of local bus types without departing from theprinciples of the invention. If the HNM 28 resides in a device, such asin a STB, the various local buses are connected directly to a local businternal to that device.

FIG. 4 shows an exemplary embodiment of the physical layer 90 of the HNM28, including the diplexer 110, RF/Analog unit 112 (hereafter RF unit)and a modem 114. The diplexer 110 is connected to the coax outlet 26 inthe room 30 and separates the CaTV signal (frequencies 5-860 MHz) fromthe home network signal. The CaTV signal includes the broadcast video,video in demand, cable modem and all other signals that are delivered bythe Cable TV operator to the home, and return path signals, like thecable modem return channel, Interactive TV etc. The CaTV signal can passto other electronic devices in the room 30, such as a TV cable modem andan analog set-top box (STB). The home network signal passes to the RFunit 112.

The RF unit 112 includes a diplexer 116, which is connected to adownstream path 118 (here, from the backbone 20 to the local bus 35) andan upstream path 120 (from the local bus 35 to the backbone 20). Fromthe home network signal, the diplexer 116 and filters 122, 142 separatethe downstream signal from the upstream signal. The downstream signalpasses towards the local bus 35 and the upstream signal towards thebackbone 20.

The bandpass filter (BPF) 122 filters the downstream signal (lowerfrequencies) to remove the upstream signal and out-of-band noise. Thedownstream signal passes through a low noise amplifier 124 and RFdown-conversion circuitry 126. The RF down-conversion circuitry 126converts the downstream signal to baseband frequencies. Embodiments ofthe RF down-conversion circuitry 126 include an I/Q demodulator or amixer.

If the RF down-conversion circuitry 126 is operating as an I/Qmodulator, the I-channel and Q-channel pass separately to the broadbandfilter/amplifier unit 128, which low-pass filters the I-channel andQ-channel separately to remove the image of the signal. The I-channeland Q-channel then pass through a dual analog-to-digital (A/D) converter129. The dual A/D 129 has a separate A/D converter for the I-channel andfor the Q-channel. The digital output of the A/D converter 129 entersthe modem 114. The modem 114 includes a digital signal processing (DSP)portion 130 and a framer 132.

In general, the modem 114 uses an efficient modulation scheme, like QAM,multi QAM, Orthogonal Frequency Division Multiplexing (OFDM) or DiscreteMultitone (DMT). In one embodiment, the backbone 20 supports 100 Mbpsbit rate. If, for example, the modem 114 uses QAM 256 (8 bits persymbol), only 12.5 MHz (100/8) of bandwidth is required. The use ofefficient bandwidth modulations achieves higher data rates for aspecific frequency band produces less cross talk between potentiallyinterfering signals. Another advantage is that the modem 114 enables thehome network 10 to coexist with pre-existing low-quality splitters oftenfound in the cable networks of the home. Such splitters are frequencylimited—at frequencies above 1000 MHz the performance of such splittersdegrades significantly. Reflections can occur at the splitter, resultingin inter-symbol interference to the home network signal.

The upstream path 120 passes from the modem 114 to the diplexer 116through a dual D/A converter 134, a baseband filter/amplifier unit 136,RF up-conversion circuitry 138, an amplifier 140, and a band-pass filter142. On the upstream path 120, the DSP 130 generates one or two outputwords corresponding to one or two D/A converters 134, depending upon theembodiment of the RF up-conversion circuitry 138. Embodiments of the RFup-conversion circuitry 138 include an I/Q modulator or a mixer. If I/Qmodulation is used in the RF up-conversion circuitry 138, then twooutput channels are implemented, with two D/A converters 134. If themixer is used, then only one D/A converter 134 is needed.

The analog baseband signal generated by the D/A converters 134 passesthrough baseband filters 136 and then is up-converted by the RF upconversion circuitry 138 to the upstream frequency band. The poweramplifier 140 amplifies the RF up-converted signal and the bandpassfilter 142 filters the signal and the diplexer 116 combines the upstreamsignal with the CaTV signal for transmission over the home coax backbone20. The gain of the amplifiers 124 and 140 are programmable, and themodem DSP 130 sets this gain.

FIG. 5 shows two embodiments of the modem 114, including the DSP 130 andthe framer 132. Signals take two paths through the modem 114; thedownstream path 118 from the dual A/D converter 129 to the MAC 92through the framer 132 and the upstream path 120 from the framer 132 tothe dual D/A converter 134.

In FIG. 5, two embodiments of the modem 114 are shown. In a firstembodiment, I/Q modulation occurs at the RF unit 112. This embodimentincludes an I/Q compensation block 144 (shown in phantom) thatcompensates digitally for different I/Q modulation imperfections, suchas local oscillator leakage, I/Q phase and amplitude imbalance, and DCsignal components. The I/Q compensated signal passes to receiverfront-end circuitry 146, which includes a match filter and aninterpolator (both not shown). The match filter filters noise and otherundesired out-of-band signals. The interpolator outputs a signal that issampled at an integer multiple of the received sample rate based ontiming recovery information received from a timing VCO block 148 and atiming PLL block 150 provide. The timing recovery is useful because theA/D converter 129 samples the downstream signal at its particularsampling frequency, which approximates but may not equal the symbol rateof the HNM 28 that transmitted the signal.

In a second embodiment of the modem 114, I/Q modulation occurs at theDSP 130 of the modem 114 (because the RF unit 112 uses a standard mixer;thus, this embodiment has no I/Q compensation block 144. Also, thereceiver front-end 146 of this embodiment includes a down-converterblock and low-pass filter (both not shown) to perform the I/Qdemodulation.

The output of the receiver front-end 146 passes to a burst AGC block152, which provides digital gain control per burst to optimize thesignal level at the input to the equalizer 154. From the burst AGC block152, the signal passes to a decision feedback equalizer (DFE) 154. TheDFE 154 includes a feed forward equalizer (FFE) 156 and a decisionfeedback filter (DFF) 158. To overcome frequency offset between thetransmitting and receiving HNMs 28, the DFE 154 includes a rotator 160,which is applied at the output of the FFE 156. A carrier recovery PLL162 sets the correction frequency of the rotator 160. The output of therotator 160 minus the output of the DFF 158 enters a slicer circuit 164to make a decision on the received symbol. The error signal 166 is equalto a distance between the decided symbol and the input to the slicercircuitry 164. The error signal 166 gives an indication to the amount ofnoise and the quality of the received signal and decisions. The errorsignal 166 is also used for the adaptation of the equalizers duringpacket receiving. The received symbols sent to the framer 132 forde-mapping, de-forward error correcting (FEC), and de-framing, toextract the transmitted data bits, which are delivered to the MAC(Medium Access Controller) 92 for upper layer processing.

On the upstream path 120, the framer 132 receives data bits from the MAC92, which frames the bits. A mapper 170 maps the encoder-framed bits togenerate the transmitted QAM symbols. A transmitter front-end 172processes the QAM symbols. The transmitter front-end 172 includes apulse shaper 174, a digital power gain adjuster 176 for fine tuning thetransmitted power, and a clipper 176 to reduce the peak-to-average ratioof the transmitted signal to relax RF transmitter requirements. Aninterpolator 180 synchronizes the transmitted symbol rate with thesymbol rate of the master HNM 28. The modulator timing VCO loop 182performs the synchronization.

Because QAM symbols are complex numbers, the signal leaving theinterpolator 180 is a complex signal, that is, the signal is made of twostreams of data (a real channel and an imaginary channel). If the DSP130 is implementing I/Q demodulation, the DSP 130 includes an I/Qfrequency up-converter 184 to create a real signal. An inverted-sinefilter 186 then shapes the resulting I/Q signal band and delivers theshaped signal to the D/A converter 134.

If the DSP 130 is not implementing I/Q demodulation, because the RF unit112 is performing the I/Q demodulation, the I/Q frequency up-converter184 is not used. The signal from the interpolator 180 remains complexand the dual D/A converter convert the two (real and imaginary) signalstreams into two analog channels (I and Q). Also, in this embodiment, atransmitter I/Q compensator 188 is employed to handle RF imperfections.

The DSP portion 130 of the modem 114 also includes a preamble detectorand channel estimation block 190 (hereafter preamble detector), which iscommunication with the I/Q compensation block 144 (if any), the receiverfront-end 146, a cycle start detector 192, and the burst AGC block 152.The preamble detector 190 also controls the gain of the amplifiers 124and 140 of the RF unit 112 to provide power control, as described above.The preamble detector 190 provides channel estimations, RF imperfectionestimations, and synchronization information for the PLL loop 150. Thepreamble detector 190 initializes the DFE 154 for each burst. Otherfunctions of the preamble detector 190 include detecting an existingburst in the downstream path 118, distinguishing between types of bursts(described below), and detecting a cycle start signal. Depending uponthe type of burst detected, the modem 114 adopts a different behavior.

The MAC (FIG. 3) layer 92 controls the transmission protocol (hereafterMAC protocol) by which the HNMs 28 communicate with each other over thecoax backbone 20. In the home network, one of the HNMs 28 connected tothe coax backbone 20 is designated as a master HNM 28. In oneembodiment, such designation can occur by manually configuring that oneHNM 28 to operate as the master HNM 28. In another embodiment, the HNMs28 elect the master HNM 28. Functionality of the master HNM 28includes: 1) assigning addresses to each of the HNMs 28 and devices inthe home network; 2) synchronizing the HNMs 28; 3) managing isochronousand asynchronous transmissions over the backbone 20 to avoid collisionsbetween transmitting HNMs 28; 4) allocating bandwidth to the HNMs 28;and 5) registering new HNMs 28. Also, a master HNM that is incorporatedin or in communication with a STB (or other device that has access tothe cable head-end) operates as a window into the home network throughwhich someone at the cable head-end can monitor and diagnose theoperation of the home network 10.

Communication on the coax backbone 20 between HNMs 28 is isochronous orasynchronous, in accordance with the MAC protocol. To exchange messageswith each other, the HNMs 28 transmit isochronous and asynchronousbursts over the backbone 20. Each burst has a predefined structure(described below) that encapsulates one or more packets. The header ofthe packets includes the destination address of the target device forthat packet—each packet has its own destination). The data in suchpackets convey the messages (i.e., the meaning of the communications).The devices 33 on the local buses 35 produce and send the packets to theappropriate HNM 28 to be prepared into bursts. A single burst caninclude packets that originate from more than one device 33 on a localbus 35 or that are targeted to more than one device 33 on a local bus35. In general, the MAC protocol ensures that bursts transmitted bydifferent HNMs 28 over the backbone 20 do not collide, or if collisionsdo occur because of errors or noise over the backbone 20, the homenetwork can recover and resume normal operation.

The MAC protocol supports at least seven types of bursts: 1) cycle startbursts; 2) data bursts; 3) registration start bursts; 4) registrationbursts; 5) fairness cycle start bursts, 6) empty bursts, and 7)self-train bursts, each described in more detail below. Only the masterHNM 28 issues cycle start, fairness cycle start, and registration startbursts.

The cycle start burst indicates the start of an isochronous cycle and ofa transmission cycle (described below). Each cycle start burst carriesCSR data of the master HNM 28. The CBR data in the cycle start burst caninclude management data, an identity of each HNM 28 that is going totransmit a data burst during the upcoming CBR period 228, and atransmission order for the HNMs 28 to follow during the CBR period 228.The other HNMs 28 in the home network 10 synchronize to this cycle startburst.

Fairness cycle start bursts mark the start of a fairness cycle (and aUBR period). Registration start bursts indicate a beginning of aregistration period that is available for a new HNM 28 to use, asdescribed below.

Any HNM 28, including the master HNM 28, can issue data bursts, emptybursts, and self-train bursts. Data bursts carry data and managementinformation. Empty bursts carry no data. A HNM 28 transmits an emptyburst when it has no data to transmit during its allotted time. Themaster HNM 28 transmits an empty burst if another HNM 28 does not useits allotted time (and does not issue an empty burst). Self-train burstsoperate to calibrate the HNM 28 to the transmission characteristics ofthe home network.

HNMs 28 other than the master HNM 28 issue registration bursts toregister with the master HNM 28, and thus with the home network 10.Within the registration burst, the registering HNM 28 can request aguaranteed bandwidth and indicate the amount of bandwidth desired.

FIG. 6 shows an exemplary embodiment of the structure of each burst 200that the HNMs 28 transmit over the coax backbone 20. Each burst 200 is asequence of segments that includes a preamble 202 (having a periodicpreamble 210 and an aperiodic preamble 212), a Phy header 204, data 206,and a postamble 208.

The preamble 202 signifies the start of the burst 200 and the type ofburst 200. In general, the preamble 202 enables the modem 114 of the HNM28 to synchronize the carrier and timing loops 162, 150, respectively,and the equalizers 156, 158 to the transmitted burst 200. The preamble202 also enables the setting of the gains of the analog amplifiers 124,140 in the RF unit 112.

The periodic preamble 210 is a predetermined sequence that enables themodem 114 within the HNM 28 to achieve carrier sense, carrier and timingsynchronization, received-power level estimation, and initial channelestimation. In one embodiment, the length of the periodic preamble 210indicates the type of burst. The length is determined by the number oftimes a sequence of symbols (e.g., 32 symbols) is repeated. For example,in one embodiment, if the 32-symbol sequence is repeated 4 times thenthe burst is a data burst, 6 times means that the burst is a cycle startburst, 8 times indicates a fairness cycle start burst, and 10 timesindicates a registration start burst.

The pattern of symbols in the periodic preamble 210 can also be used toindicate the type of burst. For example, two different burst types canhave the same periodic preamble length, but be distinguished bydifferent symbol patterns (e.g., inverting the sign of the signal forevery other repeated symbol sequence). For example, in the embodimentdescribed above, the periodic preamble of the empty burst has a 32symbol sequence that is repeated four times, which is the same length asthe periodic preamble of the data burst. Also, for the self-train burstthe 32-symbol sequence is repeated 8 times, which is the same length asthe periodic preamble of the cycle start burst. For the empty andself-train bursts, however, the sign alternates for every other repeatedsymbol sequence, which distinguishes these bursts from the data andcycle start bursts (which do not use an alternating sign), respectively.

There are two classes of bursts: bursts that require channel estimationand bursts that do not. Bursts that require the channel estimation bythe receiving HNM 28 include data bursts, cycle start bursts, fairnessstart bursts, registration bursts, and registration start bursts. Eachof these burst types has a preamble 202 of a fixed length; that is,cycle start bursts have a preamble of a first fixed length, fairnessstart bursts have a preamble 202 of a second fixed length, etc. Thedistinguishing of burst types by the length of the preamble 202 assuresthat the receiving HNM 28 achieves real-time performance without theneed for extended complexity and buffering. For attaining real-timeperformance, encoding the burst type by the periodic preamble length ismore advantageous than embedding the burst type in the header, as is theusual practice with lower rate systems. Encoding the burst type by theperiodic preamble length rather than embedding the burst type in theheader avoids a time consuming process of extracting the data embeddedin the header to determine the burst type.

Bursts that do not require channel estimation include empty (or null)bursts and self train bursts, which in general have a shorter preamble202 than the other types of bursts. As described above, the periodicpreamble 210 of the preamble 202 for these bursts have an alternatingsign (signals of the odd periods are the inverse of signal of the evenperiods). Although not useful for channel estimation, this type ofpreamble 202 is useful for burst type identifications.

The modem 114 uses the predetermined aperiodic preamble 212, which is apseudo-random sequence, to refine the channel estimation and toinitialize the modem equalizers 154, 156.

The Phy header 204 includes the parameters that are required by the DSP130 and FEC 132 to decode the bursts (i.e., a scrambler seed, FECparameters, interleaver parameters, constellation sizes, etc.). In someembodiments, the Phy header 204 also includes the source address of eachdevice 33 originating the burst. In one embodiment, the Phy header 204conveys 36 bits of information on 18 QPSK (Quadrature Phase ShiftKeying) symbols.

The data 206 carries the QAM symbol data. The constellation is the samefor each HNM 28 (when transmitting), except when the HNM 28 istransmitting a registration burst. (Registration bursts are always QPSK,which is the default constellation size for new HNMs 28 requesting tojoin the home network 10.)

The postamble 208 is a predefined sequence of BPSK (Binary Phase ShiftKeying) symbols that the modem 114 uses (along with any gap that followsthe burst 200) to recognize as the end of the burst 200.

FIGS. 7A-7C show an embodiment of an exemplary sequence 220 of bursts,separated by transmission gaps, produced by four HNMs 28 (HNM 0, HNM 1,HNM 2, and HNM 3) on the coax backbone 20 in accordance with the MACprotocol. Transmission of the bursts over the backbone 20 occurs as asequence of cycles. Each cycle carries information that enables the HNMs28 to recover timing and other parameters accurately for the successfulreceiving and transmitting of bursts.

As shown, the sequence of cycles includes three types of communicationcycles, 1) transmission cycles 222, 2) fairness cycles 224, and 3) ACKcycles 226, and four types of periods, 1) constant bit rate (CBR)periods 228, 2) unspecified bit rate (UBR) periods 230, 3) registrationperiods 232, and 4) ACK periods 226.

Each transmission cycle 222 starts when the master HNM 28 transmits acycle start burst and ends before the master HNM 28 transmits the nextcycle start burst. Each transmission cycle 222 has a predeterminedduration (e.g., approximately 1 ms) and starts with a CBR period 228.During this CBR period 228, each HNM 28 that has been allocatedbandwidth by the master HNM 28 transmits one CBR burst. (CBR bursts caninclude one or more CBR packets aggregated together and transmittedduring the CBR period.) Each HNM 28 that has been allocated time withinthe CBR period 228 transmits one burst, but the size (or length) of thatburst depends upon the amount of bandwidth allocated to that HNM 28 andupon the amount of data ready for transmission in that particulartransmission cycle. If at a particular transmission, the HNM 28 does nothave any data ready for transmission, the HNM 28 transmits an empty (ornull) burst. This empty burst notifies the next HNM 28 in thetransmission order that the next HNM 28 can now transmit during the CBRperiod 228. The HNMs 28 transmit bursts over the backbone 20 in an orderpredefined by the master HNM 28. For example, as shown in FIG. 7, thetransmission order during each CBR period 228 is HNM0 (the master HNM)followed by HNM1 and then by HNM3. (In this example, HNM2 has noallocated bandwidth during the CBR period 228.) The master HNM 28 canchange the amount of allocated bandwidth and the order of transmission,such as when a new HNM 28 registers for guaranteed quality of service.The master HNM 28 communicates such changes to the other HNMs 28 in thedata field 206 of the cycle start burst.

If, at the end of the CBR period 228, time remains in the currenttransmission cycle, a UBR period 230 or a registration period 232 and/oran ACK period 226, follows the CBR period 228. The UBR period 230 ispart of a fairness cycle 224, as described below. During the UBR period230, each HNM 28 can send a self-calibration (or training) burst beforesending a UBR burst. (A UBR burst is a burst that is transmitted duringthe UBR period 230.)

A fairness cycle 224 represents the time over which every HNM 28transmits one UBR burst over the coax backbone 20. (If a HNM 28 has nodata to transmit, the HNM 28 transmits a null burst in its allottedtime.) The fairness cycle 224 can span one or more transmission cycles222. Accordingly, during a fairness cycle 224, UBR periods 230 areinterleaved with CBR periods 228.

More specifically, each fairness cycle 224 begins with a UBR burst fromthe master HNM 28 (called a fairness start burst) and completes afterall of the other registered HNM 28 transmits a UBR burst. The HNMs 28transmit the UBR bursts according to a certain order, starting with themaster HNM 28 (here, HNM 0). The UBR bursts do not disturb thesynchronization of the transmission cycle; that is, transmission cycles222 and, thus, CBR periods 228, occur regularly (with some jitter,described below), even if each registered HNM 28 has not yet transmittedan UBR burst. (In such an instance, a fairness cycle 224 spans more thanone transmission cycle 222.) Jitter occurs when one of the HNMs 28 ispresently transmitting a UBR burst while the start of a new transmissioncycle 222 is due to begin. Instead of starting the new transmissioncycle 222, the HNM 28 is permitted to complete the UBR burst, whichextends the present transmission cycle 222 beyond the predefinedtransmission cycle period. Jitter is the measure of the amount of timethat the UBR period extends beyond the expected end of the transmissioncycle 222 (i.e., start of the next CBR period 228).

At the end of a fairness cycle 224, the master HNM 28 transmits aregistration start burst to initiate a registration period 232, whichextends for a predefined period. (The registration start burst marks theend of the fairness cycle 224.) The master HNM 28 determines when tostart the registration period 232. In some embodiments, a registrationperiod 232 can occur as often as after each fairness cycle 224. In otherembodiment, the registration period 232 occurs less frequently, such asafter a plurality of fairness cycles 224. As described above, generally,with respect to UBR periods 230, the registration period 232 can extendbeyond the end of the current transmission cycle 222, thus delaying thestart of the next transmission cycle 222.

The registration period 232 is available for use by new HNMs 28 (i.e.,HNMs 28 that have been added to the home network and have not yetparticipated in network communications). During the registration period232, new HNMs 28 register with the master HNM 28, transmit a self-trainburst to adapt the Phy parameters, and if already calibrated, transmitsa registration burst. An HNM 28 that transmits a registration burstsexpects to receive from the master HNM 28, in a subsequent cycle startburst, a response that includes a new identity for the registering HNM28 and a position in the UBR transmission order in which to transmit UBRbursts.

During a given registration period 232, more than one HNM 28 mightattempt to register with the master HNM 28. Accordingly, collisionsbetween HNMs 28 can occur. However, the number of HNMs 28 participatingin any given registration period 232 is typically few; thus, thelikelihood of collisions on the home network 10 is generally low. Also,colliding HNMs 28 that do not successfully register during the presentregistration period 232 retransmit the registration request during asubsequent registration period 232. Each HNM 28 independently andrandomly determines the number of registration cycles to wait beforeretransmitting a registration request. This random and independentretransmission reduces the likelihood that the colliding HNMs 28 willcollide again. Further, each HNM 28 that successfully registers during agiven registration period 232 does not communicate during subsequentregistration periods (subsequent transmissions by successfullyregistering HNMs 28 occur during the time slot allocated to that HNM28).

During a registration period 232, the master HNM 28 receives theregistration bursts, if any, from new HNMs 28. During the CBR period 230immediately following the registration period 232, the master HNM 28responds to one of the registration bursts with a cycle start burst thatincludes a master management message within the data field 206 of thecycle start burst. The master management message indicates to theregistering HNM 28 where that HNM 28 appears in the transmission orderduring the CBR period 230 and, if required, the amount of bandwidth thathas been allocated to the HMN 28.

If the master HNM 28 receives more than one registration request, themaster HNM 28 responds to only one of the registration requests, and theother registering HNMs 28 retransmit during a subsequent registrationperiod as described above. The master HNM 28 identifies the HNM 28 towhich the master is responding in the Phy header 204 of the cycle startburst.

When the registration period 232 times out, the master HNM 28 transmitsan ACK burst, marking the start of an ACK period 226 (or cycle). In oneembodiment, the first ACK burst (i.e., ACK0) marks the start of the ACKperiod 226. In another embodiment, the registration start burst marksthe start of the ACK period 226. During the ACK period 226, each HNM 28,starting with the master HNM 28, transmits an ACK corresponding to theUBR bursts during the previous fairness cycle 224.

ACK bursts are used for UBR traffic. Each HNM 28 sends an acknowledgemessage (ACK) for each burst that the HNM 28 receives. If thetransmitting HNM 28 does not receive an acknowledgement from one of thedestinations, it retransmits the packets. Using acknowledgment messagesimproves the performance of the home network 10 in cases of noise thatcorrupt some burst traffic. Each burst is an aggregation of packetsdestined for one or more destinations. If an ACK is not received fromone or some of the destinations in the burst, the messages correspondingto the unacknowledged packets are retransmitted.

After the ACK period 226, a gap can appear in the communications on thecoax backbone 20 when the master HNM 28 is still processing the last ACKburst of the ACK period 226. Then, the master HNM 28 marks the en theend of the ACK cycle and the start of the next fairness cycle 224 bytransmitting a UBR burst. If the expected time for the start of the nexttransmission cycle 222 arrives, the master HNM 28 transits a cycle startburst.

FIGS. 8A-8B show an embodiment of a process by which the master HNM 28controls communication on the coax backbone 20. To mark the beginning ofa transmission cycle 222, the master HNM 28 sends (step 240) a cyclestart burst onto the backbone 20. The cycle start burst can includemaster management data, an identity of each HNM 28 that is going totransmit a data burst during the upcoming CBR period 228, and atransmission order for the HNMs 28 to follow during the CBR period 228.The listed identities are of those HNMS 28 that have requested from themaster HNM 28 a guaranteed bandwidth. In one embodiment, the cycle startburst includes information regarding the HNMs 28 that are to transmit aUBR burst during the transmission cycle, such as a transmission order.In another embodiment, the cycle start burst also includes the CBRtransmission order information.

The master HNM 28 monitors (step 242) the backbone 20 for CBR bursts.

When the master HNM 28 determines that the CBR period 228 has ended, andif a previous ACK cycle 224 has ended, the master HNM 28 issues (step246) a UBR burst to start a new ACK cycle. The master HNM 28 monitors(step 248) the backbone 20 for subsequent UBR bursts. The master HNM 28maintains (step 250) a timer to determine when the present transmissioncycle 222 is to end. When the timer indicates the end of thetransmission cycle 222, the master HNM 28 starts the next CBR period 228by issuing (step 252) a cycle start burst. Before issuing the cyclestart burst, the master HNM 28 waits for any burst in progress tocomplete.

When the master HNM 28 determines (step 254) that the current fairnesscycle 224 has ended, the master HNM 28 transmits (step 256) aregistration start burst to initiate a registration period 232. (In oneembodiment, the master HNM 28 can skip one or more fairness cycles 224before initiating the registration period 232.) During the registrationperiod 232, the master HNM 28 receives (step 258) zero, one or moreregistration requests. The master HNM 28 replies (step 260) to oneregistration request during the next CBR period.

The master HNM 28 maintains (step 266) a timer to determine when theregistration period ends. When the timer indicates the end of theregistration period, the master HNM 28 sends (step 268) an ACK burst tomark the start of the ACK cycle. During the ACK cycle, the master HNM 28determines (step 270) when the present transmission cycle ends andissues (step 272) a cycle start burst to start the next CBR period 228.In one embodiment, the master HNM 28 waits until the ACK cycle endsbefore sending the cycle start burst. Also during the ACK cycle, themaster HNM 28 monitors (step 274) the backbone 20 for ACKs from theother HNMs 28. Upon detecting completion of the ACK cycle, includingwaiting for an ACK for its own UBR burst (i.e., if the ACK was requestedin that UBR burst), the master HNM 28 issues (step 276) a UBR burst (afairness cycle start burst) to start a new fairness cycle or a cyclestart burst to start a new transmission cycle if the expected time tostart a new transmission cycle has arrived.

FIG. 9 shows an embodiment of a process by which each HNM 28 in the homenetwork, other than the master HNM 28, communicates over the coaxbackbone 20. In step 280, the HNM 28 receives a cycle start burst anddetermines from the cycle start burst its positions in the transmissionorders for CBR and UBR and its allocated amount of bandwidth. The cyclestart burst operates to synchronize communications between the HNM 28and the master HNM 28. The HNM 28 monitors (step 282) the backbone 20for CBR bursts, and after waiting for its own allotted time in the CBRtransmission order, if any, transmits (step 284) a CBR burst. Bymonitoring the backbone 20 for CBR bursts, the HNM 28 determines whenthe CBR period is over (each HNM 28 can determine the list of HNMs 28participating in the CBR period from the information provided by cyclestart burst).

After the CBR period 228 ends, the HNM 28 determines (step 286) whetherit can transmit a UBR burst. To be enabled to transmit a UBR burst, inone embodiment the HNM 28 requires (step 288) a grant from the HNM 28that precedes it in the transmission order. After transmitting the UBRburst, the grant passes (step 290) to the next HNM 28 in the UBRtransmission order. In another embodiment, the HNM 28 awaits its turn(step 288′) to transmit the UBR burst by monitoring the backbone 20 andcounting the number of UBR bursts that were transmitted since the startof the current fairness cycle 224.

In step 292, the HNM 28 detects an ACK burst (or in one embodiment aregistration start burst) on the backbone 20, marking the start of anACK cycle. The HNM 28 determines (step 294) when to transmit the ACKbased on its position in the transmission order. If the HNM 28 has anACK to transmit (depending upon whether it received a UBR requesting anACK during the previous fairness cycle), the HNM 28 transmits the ACK;otherwise the HNM 28 transmits an empty (null) burst. The HNM 28 canmake this determination by monitoring the backbone 20 for ACK bursts orby waiting to receive a grant from the HNM 28 immediately preceding inthe UBR transmission order.

FIG. 10 shows an embodiment of a process by which a new HNM 28 becomespart of home network 10. Upon detecting (step 296) a registration startburst, the new HNM 28 issues (step 298) a Self_Train Burst (forcalibrating its PHY) or a registration request. If the new HNM 28 doesnot receive a reply indicating that the master HNM 28 has registered thenew HNM 28, the new HNM 28 transmits (step 298) another registrationrequest in a subsequent registration period. The new HNM 28 continues totransmit registration requests during subsequent registration periodsuntil the new HNM 28 becomes registered. In one embodiment, the new HNM28 randomly selects how many registration periods to skip beforeretransmitting the registration request. After becoming registered, thenew HNM 28 transmits bursts during the UBR period as described above.

Referring back to FIG. 1, the home network includes a plurality of localbuses 35 each connected to the coax backbone 20 network by an HNM 28.One of the HNMs 28 is the master HNM 28, and the local bus 35 that isconnected to the master HNM 28 is the prime bus. If the same HNM 28connects multiple local buses 35 to the coax backbone 20, each local bus35 is of a different type (e.g., 1394, Ethernet, USB); if that HNM 28 isthe master HNM 28 of the home network 10, then each of such local buses35 is deemed to be the prime bus (of its particular type).

FIG. 11 shows one embodiment of the home network 10, in which thebackbone 20 connects four IEEE 1394 local buses through different HNMs28. In this embodiment, each HNM 28 shown operates as a 1394-to-coaxbackbone bridge between the backbone 20 and the 1394 local bus connectedto that HNM 28. Devices 33 that are connected to one of the 1394 busesare referred to as 1394 devices or nodes. Although the backbone 20appears as a ring, this is for purposes of showing that the HNMs 28 areconnected to the backbone 20, and not intended to show that the backbone20 operates as a ring network.

There are two embodiments of the 1394-to-coax bridge. In a firstembodiment, each bridge operates according to the IEEE 1394.1 standard.In a second embodiment, the bridge emulates the plurality of 1394 busesas a single bus so that nodes connected to these 1394 local buses cancommunicate with each other as though on the same 1394 bus (i.e., usingthe short haul 1394 protocol).

For the second embodiment, to achieve the appearance that all 1394devices in the home network are residing on the same 1394 short haulbus, modifications are made to the 1394a Phy and Link layers 102, 104.In brief, the modifications include the following:

-   -   1) at the Phy layer 102, modifications to the reset,        initialization, and identification processes enable device (or        node) discovery throughout the home network 10; and    -   2) at the Link layer 104, the addition of routing tables (in one        embodiment, one table is for isochronous traffic, and another        table is for asynchronous traffic, in another embodiment, one        routing table handles both traffic types.) and the forwarding of        packets (incorporated within bursts) to the coax backbone 20        enable delivery of such packets to remote buses over the        backbone 20.

The Link layer 104 uses the asynchronous routing table to determinewhether the destination identifier of an asynchronous packet is on aremote bus (other than the local bus from which the packet originates).If the destination is on a remote bus, the Link layer 104 sends anACK_pending packet to the originator of the packet (i.e. source node)and forwards the asynchronous packet to the backbone 20. The HNM 28incorporates the asynchronous packet within a burst, which can includesother packets targeted to other destinations. If the destination is noton a remote bus, the Link layer 104 operates as a standard Link layer toprocess the asynchronous packet.

Asynchronous packets between devices on the same local bus 35 remainlocal to that bus 35. The HNM 28 does not forward such packets to thebackbone 20. The HNM 28 routes asynchronous packets destined to a remotedevice according the asynchronous routing table that resides in that HNM28 and responds to the packet by sending an ACK_pending packet to thepacket originator). The asynchronous routing table defines remote HNMs28 according to the Phy_ID in the asynchronous packet destination field.The HNM 28 forwards isochronous channel packets and asynchronous streamsthrough the backbone 20 to all the other buses or to other busesaccording to the isochronous routing table. One clock reference existsfor the home network 10. The prime bus generates the common clock, whichthe HNMs 28 connected to at the other buses each recover.

Referring again to FIG. 11, each local 1394 bus has the followingfeatures. Each 1394 node receives a unique Phy identification number(Phy_ID) (0-62), and each HNM 28 receives the same Phy_ID number (anumber that is unique from those assigned to the nodes). For each localbus 35, the bus identification number (Bus_ID) is equal to 0x3FF. Thehome network 10 has one Isochronous Resource Manager (IRM), which is oneof the HNMs 28, typically the master HNM 28. Each isochronous channeland each asynchronous stream that is generated in the home network 10receives its channel number and bandwidth allocation from the singleIRM. Each local 1394 bus 35 has its own Cycle Master, which is the HNM28 of that bus. Each local bus 35 has its own Bus Manager. Arbitration,signaling and data transfers are local to each local bus 35.

Each HNM 28 performs various operations to cause the other remote busesto appear as though on its local bus, Such operations include:

-   -   1) sending self-identification (Self_ID) packets according to a        reset procedure used for discovering 1394 nodes;    -   2) forwarding streams through the backbone 20, with updating        timestamp of 61883 isochronous packets (the 61883 is a standard        that specifies transport of MPEG signals over the 1394 and        allows the video transfers between 1394 devices);    -   3) sending acknowledge pending (ACK_pending) packets to the        source of asynchronous packets that are to be delivered to other        remote buses according to the asynchronous routing table        (responding with an ACK_pending packet satisfies a 10 uSec        requirement for ACKs in standard 1394 communications, although        an acknowledgement issued by the target of the packets can        experience a latency over the backbone 20 of greater than 10        uSec);    -   4) forwarding asynchronous packets that are to be delivered to        other remote buses through the backbone 20 according to the        asynchronous routing table;    -   5) receiving asynchronous packets over the backbone 20 from        other remote buses targeted to a device on the local bus of the        HNM 28; and    -   6) distributing a reset that occurs on one bus to the other        buses.

To initialize the home network 10, the HNMs 28 perform a global resetprocess. During the global reset process, the home network 10 conductsan initialization and identification process. As a result, an emulatedbus structure is created where all 1394 devices in the network 10 seeeach other, and each 1394 device has a unique Phy_ID. After the end ofinitialization and identification processes, each HNM 28 appears us aroot 1394 node with three Phy ports.

FIG. 12 is an embodiment of the emulated bus structure from theperspective of each of the HNMs 28. Each HNM (HNM1, HNM2, HNM3, HNM4) isa root node for its respective local bus. Port 1 (P1) of each HNM 28 isconnected to the local bus. Phy port 0 (P0) and Phy port 2 (P2) appearto all 1394 devices on the local bus either as not connected or as abranch of the bus. The branch appears to contain other 1394 devices thatare physically located in other buses but logically appear to the localbus devices as if they are reside on the same bus. For example, for HNM1, the P0 port appears as unconnected, the P1 port is connected to thephysical bus of HNM1, and the P2 port is an emulation of the other localbuses in the home network 10, namely, remote buses of HNM 2, HNM 3, andHNM 4. As another example, for HNM 2, the P0 port is an emulation of theremote bus of HNM 1, the P1 port is connected to the physical bus ofHNM2, and the P2 port is an emulation of the remote buses of HNM 3, andHNM 4. Thus, all existing 1394 devices in the network seemingly resideon the same bus. Therefore, any application that works with 1394 busesis supported over the entire home network 10.

Each HNM 28 generates two types of self-ID packets: 1) HNM 28 self_Dpackets, and 2) emulated self-ID packets. HNM self-ID packets issued byeach HNM 28 describe the three-port root node (shown in FIG. 12) forthat HNM 28. Emulated self-ID packets describe all nodes on the otherHNM local buses. Each emulated self-ID packet represents the busstructure of two port nodes (P0 and P2) that are connected serially tothe root node as one branch.

Initialization of the home network 10 occurs after the backbone 20 hasbeen initialized, that is, the number (N) of HNMs 28 is known, each HNM28 has its own number (1 through N), and a master HNM 28 is selected.When the initialization ends, the home network 10 is operational.

Referring to FIG. 13, during initialization, the master HNM 28 sends(step 304) through the backbone 20 a first global reset packet to allthe HNMs 28. The reset is performed (step 308) in each bus with the root(i.e., the appropriate HNM 28) governing the reset process. After thereset, each HNM 28 sends (step 312) an updating bus message to themaster HNM 28. The updating bus message includes: 1) the Phy_ID of theHNM 28 (i.e., the number of nodes on the bus −1); 2) the link state(active/not active) for each node on the local bus, and 3) an indicatorfor each node on the local bus whether that node is “bridge capable.” (A“bridge capable” device is a 1394 device that is compliant with the IEEE1394.1 standard.) Also, after the reset, each bus functions locally.

From the updating bus messages obtained from the HNMs 28, the master HNM28 generates (step 316) a network table. For each HNM 28, the networktable includes the number of nodes in the local bus of that HNM 28, thelink status (active/inactive) of each node in the local bus of that HNM28, and the bridge capabilities for each node in the local bus of thatHNM 28. After producing the network table, the master HNM 28 transmits(step 320) the network table to each HNM 28 using anupdate_network_table message. The update_network_message includes thetime for generating the next bus reset. Each HNM 28 updates (step 324)its own network table accordingly.

At the time specified in the update_network_table message, each HNM 28generates (step 328) a bus reset. After the network completes theinitialization, the home network undergoes a network update process. Instep 332, if there are no topology changes in the local bus, the resetis not propagated to other buses. After the local bus reset sequence iscompleted and the HNM 28 port obtains its new Phy_ID, this informationis propagated (step 334) by a new_phy_id message to the master HNM 28.The master HNM 28 updates (step 336) the network table and sends (step340) a update_network_table message to the other HNMs 28. Upon receivingthe update_network_table message, each HNM 28 proceeds as describedabove, that is, by locally resetting the bus (step 308), updating thenetwork table (step 324), and emulating the home network 10 in that bus.

After the completion of the initialization of the home network, each HNM28 handles asynchronous packets received from the bus (inbound—upstreamfrom local bus to backbone) and asynchronous packets received from thebackbone 20 (outbound—downstream from backbone to the local bus).Although described in terms of local 1394 buses, the principles ofpacket handling applies also to other bus types, such as USB, Ethernet,etc.

FIG. 14 shows an embodiment of a process for use by each HNM 28 whenhandling inbound asynchronous packets. For inbound asynchronous packets,each HNM 28 forwards such packets to the backbone 20 based on thephysical ID (Phy ID) destination address, the physical ID of the HNM 28,and the network table. During the initialization process, each HNM 28maintains two registers, one with the Phy_ID of the node with the lowestID on its local bus and one with the highest ID on the local bus. APhy_ID between the highest and lowest IDs is on the local bus.

In step 354, If the bus ID is equal to 0x3FF, which identifies the localbus as a 1394a bus, the HNM 28 performs the following actions:

-   -   1. In step 358, if the Phy_ID is equal to 0x3F16, this indicates        that the packet is a broadcast packet. In step 362, if the HNM        28 is the master HNM 28, then the HNM 28 forwards (step 366) and        processes (step 370) the packet. If the HNM 28 is not the master        HNM 28, then the HNM 28 forwards (step 374) the packet. In this        instance, the non-master HNM 28 does not process the broadcast        packet, thus preventing broadcast packets from accessing        non-master HNMs 28. Access to non-master HNMs 28 is the        privilege of master HNMs 28, not devices on the local bus.    -   2. In step 378, if the Phy_ID does not correspond to a node on        the local bus, the HNM 28 forwards (step 382) the packet to the        backbone 20 and issues (step 386) an ACK_pending (busy or retry)        packet to the local bus,    -   3. In step 390, if the Phy_ID corresponds to a node on the local        bus (but not the Phy_ID of the HNM 28), the HNM 28 discards        (step 392) the packet.    -   4. In step 398, if the Phy_ID is that of the HNM 28, the HNM 28        processes (step 394) the packet if the HNM 28 is the master HNM        28, and forwards (step 396) the packet if the HNM 28 is not the        master HNM 28. Again, access to non-master HNMs 28 is the        privilege of master HNMs 28, not devices on the local bus.

If the bus ID does not equal 0x3FF, the HNM 28 forwards (step 398) thepacket and issues an ACK_pending packet to the local bus.

FIG. 15 shows an embodiment of a process for use by each HNM 28 whenhandling outbound asynchronous packets. For outbound asynchronouspackets, each HNM 28 forwards such packets from the backbone 20 to thelocal bus 35 based on the physical ID destination address, the physicalID of the HNM 28, and the network table. If addressed to the address ofthe HNM 28, a packet passes to the HNM 28 only if the source of thatpacket is the master HNM 28 (a flag in the packet can indicate that thesource of the packet is the master HNM 28).

In step 404, if the bus ID is equal to 0x3FF, the HNM 28 performs thefollowing actions:

-   -   1. In step 408, if the Phy_ID is equal to 0x3F16, this indicates        that the packet is a broadcast packet; if so, the HNM 28        forwards (step 412) the packet to the local bus.    -   2. In step 416, if the Phy_ID does not correspond to a node on        the local bus, the HNM 28 discards (step 420) the packet.    -   3. In step 424, if the Phy_ID corresponds to a node on the local        bus (but not the Phy_ID of the HNM 28), the HNM 28 forwards        (step 428) the packet to the local bus.    -   4. In step 432, if the Phy_ID is that of the HNM 28, the HNM 28        processes (step 436) the packet if the HNM 28 is the master HNM        28, and discards (step 440) the packet if the HNM 28 is not the        master HNM 28.

If the bus ID does not equal 0x3FF, the HNM 28 forwards (step 444) thepacket to the local bus.

For isochronous streams, in one embodiment, each HNM 28 forwards to thelocal bus 35 those streams that are received from the backbone 20 andforwards to the backbone 20 those streams that are received from thelocal bus 35. The HNMs 28 forward the packets in these streams as thepackets are received; that is, the HNMs 28 do not need to filter thesepackets.

FIG. 16 shows another embodiment of the DPU 14′ including a firstsplitter-combiner 460, which receives signals from and transmits signalsto the cable television/internet network 18. The splitter-combiner 460distributes those signals to the components of the DPU 14′ from thecable television/internet network 18 and collects signals from thecomponents of the DPU 14′ for transmission to the cabletelevision/internet network 18. Similarly a second splitter-combiner 464receives signals from and transmits signals to the various rooms 30through the coax cables 22. The splitter-combiner 464 distributessignals received from the various rooms 30 to the components of the DPU14′ and distributes signals from the components of the DPU 14′ to thevarious rooms 30. The embodiment shown in FIG. 11 uses the frequencyband of 5-45 Mhz for the home network signal, and the frequency band50-850 MHz for the cable TV and Internet provider signals.

The components of the DPU 14′ can be modified to achieve the otherfrequency bands described above for carrying the home network signal.

The components of this embodiment of the DPU 14′ include a high-passfilter 470 connected between the first splitter combiner 460 and thesecond splitter combiner 464. The high-pass filter 470 allows thetransparent connection of legacy TV cable network in the forward andreverse channels, while blocking the specific frequency channels thatare allocated for the internal home network signal. In one embodiment,this high-pass filter 470 has a cut-off frequency of 50 MHz, thuspermitting signals having a frequency greater than the 50 MHz high-passcut-off to pass transparently between the splitter-combiners 460, 464.Signals above this frequency are typically legacy television signals(i.e., 55-850 MHz) and therefore should pass unimpeded through the DPU14′. Frequencies lower than the cut-off are thus available for use bythe home network signal.

The DPU 14′ is responsible for allowing the RDC OOB and RDC CM signalsto pass from the set top boxes and cable modems, respectively, to thehead-end of the cable television network 18. To accomplish this, the DPU14′ includes a Forward OOB receiver and decoder 490 and a cable modem474. The cable modem 474 and Forward OOB receiver 490 receive the datafrom the OOB Forward Data Channel and decode the signal to acquireinformation concerning which frequency is to be used as the RDC OOB andRDC CM channels. A controller 492 receives the OOB information, extractsthe information on the current frequency bands that are being used inthe home, and directs the home network 10 to use other frequency bands.After this frequency information is obtained, the DPU 14′ controls thehome network 10 so that no signals are transmitted on this OOB RDC andRDC CM frequency. A notch filter achieves this control, in oneembodiment, by blocking passage of signals within the RDC OOB and RDC CMfrequency region. In another embodiment, the corresponding tones of themulti-carrier signals are silenced. A regular multi-tone transmitter(either OFDM or DMT) determines whether to transmit power on eachparticular tone. Each tone can be silenced according to a managementmessage from the controller 492. The controller 492 in the DPU 14′distributes this management message to each of the HNMs 28 identifyingthe tones that are to be silenced.

When a device 33 in the home needs to transmit data back to the head-endusing the OOB RDC or RDC CM channel, the RDC signal is intercepted bythe DPU 14′ and transmitted to the cable television network 18. This isaccomplished using an OOB regenerator (receiver/transmitter) 486.Signals received from the home devices 33 are down-converted anddemodulated, then modulated and up-converted to the required transmittedfrequency, and then transmitted to the cable television/internet network18.

The cable modem (CM) 474 provides Internet access to the home. Othertypes of access modems are also available if the Internet access isprovided on another media than the Cable networks (e.g. a DSL modem canbe used if Internet access is provided on the telephone line network).For example, a digital subscriber line (DSL) modem replaces the cablemodem 474 if a telephone network is providing Internet access. In suchan embodiment, connection between the DPU 14′ and the Internet 18 is notthrough the splitter-combiner 460, but instead is through anotherconnector such as a RJ11 connector. An alternative embodiment includesthe functionality of the cable modem in a set-top box located in thehome (in which case, the cable modem 474 is not part of the DPU 14′). Inyet another embodiment, the cable modem 474 is a standalone device (notin a set top box or in the DPU 14′. In this case, the cable modem 474 isconnected to the backbone 20 through a HNM 28

In addition, the cable modem 474 is connected to a hub/router 478 fortransmitting data to and from the Internet 18. The hub/router 478 (orbridge) provides hub and routing functionality that distributes theexternally generated data signals (Internet) and the home network signalto the HNMs 28 in the home. The hub (or bridge) and routingfunctionality can be based on an interface such as 100-Base-T Ethernet,IEEE-1394, or USB. The signals from each output port of the hub/routerare quadrature amplitude modulated (QAM) to produce QAM signals, with aprogrammable constellation size, over a pre-defined frequency range. Asan example, with a 256-QAM modulation and a symbol rate of up to 40 MHz,the available throughput can reach up to 320 Mbps. A capability to notchfilter the signal at programmable frequencies is also provided.

The QAM signal in various embodiments is either a single carrier QAM, ormulti-band QAM, which is a summation of several QAM signals withdifferent carrier frequencies. In another embodiment, the signal ismodulated as a multi-carrier signal with approximately the sameavailable throughput. The output-modulated signals are combined with theexternal cable TV signal stream and transmitted over the backbone 20 tothe various rooms 30. A Media Access Controller (MAC) 482, 482′(generally 482), located between the hub/router functionality and theQAM or multi-tone modulators provides the functionality that allows theco-existence of several data sources over the same cable (networking),e.g. arbitration, signal detection, etc.

While the invention has been shown and described with reference tospecific preferred embodiments, it should be understood by those skilledin the art that various changes in form and detail may be made thereinwithout departing from the spirit and scope of the invention as definedby the following claims.

What is claimed is:
 1. A network module, comprising: one or morecomputing devices; and a memory including instructions that, whenexecuted by the one or more computing devices, cause the one or morecomputing devices to: determine whether the network module has beenselected from a plurality of network modules of a home network tooperate as a master module for the home network, each of the pluralityof network modules being configured to operate as the master module whenselected as the master module; when the network module has been selectedfrom the plurality of network modules to operate as the master module:assign identifiers to the plurality of network modules for communicatingover the home network; receive a first signal from another networkmodule of the plurality of network modules; determine a received powerlevel of the first signal; determine a first adjustment to a firsttransmission power of the another network module of the plurality ofnetwork modules based at least in part on the received power level ofthe first signal such that transmissions of the another network moduleof the plurality of network modules arrive at the network module havinga predefined power level, wherein the first adjustment is indicative ofan attenuation of the first transmission power of the another networkmodule; and transmit a second signal to the another network module ofthe plurality of network modules, the second signal being indicative ofthe first adjustment to the first transmission power of the anothernetwork module.
 2. The network module of claim 1, wherein theinstructions, when executed by the one or more computing devices,further cause the one or more computing devices to: determine theattenuation of the first transmission power of the another networkmodule of the plurality of network modules based at least in part on thereceived power level of the first signal.
 3. The network module of claim1, wherein the second signal comprises a management message.
 4. Thenetwork module of claim 1, wherein the instructions, when executed bythe one or more computing devices, further cause the one or morecomputing devices to: when the another network module of the pluralityof network modules has been selected to operate as the master module:transmit a third signal at a second transmission power to the anothernetwork module of the plurality of network modules; receive a fourthsignal from the another network module of the plurality of networkmodules, the fourth signal being indicative of a second adjustment tothe second transmission power; and adjust, based at least in part on thefourth signal, the second transmission power for transmissions to theanother network module of the plurality of network modules.
 5. Thenetwork module of claim 4, wherein the instructions, when executed bythe one or more computing devices, further cause the one or morecomputing devices to: when the another network module of the pluralityof network modules has been selected to operate as the master module:transmit a fifth signal at the second transmission power to the anothernetwork module of the plurality of network modules.
 6. The networkmodule of claim 1, wherein the plurality of network modules arecommunicatively coupled to a coaxial transmission network.
 7. Thenetwork module of claim 6, wherein the instructions, when executed bythe one or more computing devices, further cause the one or morecomputing devices to: when the network module has been selected from theplurality of network modules to operate as the master module:synchronize the plurality of network modules; allocate bandwidth to theplurality of network modules; and manage transmissions over the coaxialtransmission network.
 8. The network module of claim 7, wherein thetransmissions comprise variable sized packets.
 9. A method for operatinga network module, the method comprising: participating, by the networkmodule, in a selection of a master module for a local area network froma plurality of network modules of the local area network, each of theplurality of network modules being configured to operate as the mastermodule for the local area network when selected as the master module andthe plurality of network modules being communicatively coupled to acoaxial transmission network; when the network module has been selectedfrom the plurality of network modules to operate as the master modulefor the local area network: assigning identifiers to the plurality ofnetwork modules for communicating over first network media of the localarea network; synchronizing the plurality of network modules; allocatingbandwidth to the plurality of network modules; managing transmissionsover the coaxial transmission network; receiving a first signal fromanother network module of the plurality of network modules; determininga received power level of the first signal; and transmitting a secondsignal to the another network module of the plurality of networkmodules, the second signal being indicative of a first adjustment to afirst transmission power of the another network module.
 10. The methodof claim 9, further comprising: when the another network module of theplurality of network modules has been selected to operate as the mastermodule for the local area network: transmitting a third signal at asecond transmission power to the another network module of the pluralityof network modules; receiving a fourth signal from the another networkmodule of the plurality of network modules, the fourth signal beingindicative of a second adjustment to the second transmission power; andadjusting, based at least in part on the fourth signal, the secondtransmission power for transmissions to the another network module ofthe plurality of network modules.
 11. The method of claim 10, whereintransmitting the third signal at the second transmission power to theanother network module of the plurality of network modules comprises:transmitting, during initialization, the third signal at the secondtransmission power to the another network module of the plurality ofnetwork modules.
 12. The method of claim 10, wherein the adjusting,based at least in part on the fourth signal, the second transmissionpower for the transmissions to the another network module of theplurality of network modules further comprises: adjusting, based atleast in part on the fourth signal, the second transmission power forthe transmissions to the another network module of the plurality ofnetwork modules such that the transmission arrive at the another networkmodule having a predefined power level.
 13. The method of claim 9,wherein the transmissions comprise variable sized packets.
 14. Themethod of claim 9, further comprising: when the network module has beenselected from the plurality of network modules to operate as the mastermodule for the local area network: communicate with a head-end devicethat is external to the local area network over second network mediathat is distinct from the first network media of the local area network.15. The method of claim 9, further comprising: when the network modulehas been selected from the plurality of network modules to operate asthe master module for the local area network determining the firstadjustment to the first transmission power of the another network moduleof based at least in part on the received power level of the firstsignal such that transmissions of the another network module of theplurality of network modules arrive at the network module having apredefined power level.
 16. The method of claim 9, wherein the firstadjustment is indicative of an attenuation of the first transmissionpower of the another network module.
 17. A computer program productcomprising instructions stored in at least one tangible non-transitorycomputer-readable storage medium, the instructions comprising:instructions to determine whether a network module has been selectedfrom a plurality of network modules of a home network to operate as amaster module for the home network, each of the plurality of networkmodules being configured to operate as the master module when selectedas the master module; when the network module has been selected from theplurality of network modules to operate as the master module:instructions to assign identifiers to the plurality of network modulesfor communicating over the home network; instructions to receive a firstsignal from another network module of the plurality of network modules;instructions to determine a received power level of the first signal;instructions to determine an attenuation between the network module andthe another network module of the plurality of network modules based atleast in part on the received power level of the first signal;instructions to determine a first adjustment to a first transmissionpower of the another network module such that transmissions of theanother network module arrive at the network module having a predefinedpower level, wherein the first adjustment is indicative of thedetermined attenuation; and instructions to transmit a second signal tothe another network module of the plurality of network modules, thesecond signal being indicative of the first adjustment to the firsttransmission power of the another network module.
 18. The computerprogram product of claim 17, wherein the instructions further comprise:when the another network module of the plurality of network modules hasbeen selected to operate as the master module: instructions to transmita third signal at a second transmission power to the another networkmodule of the plurality of network modules; instructions to receive afourth signal from the another network module of the plurality ofnetwork modules, the fourth signal being indicative of a secondadjustment to the second transmission power; and instructions to adjust,based at least in part on the fourth signal, the second transmissionpower for transmissions to the another network module of the pluralityof network modules.
 19. The computer program product of claim 17,wherein the instructions further comprise: when the network module hasbeen selected from the plurality of network modules to operate as themaster module: instructions to synchronize the plurality of networkmodules; instructions to allocate bandwidth to the plurality of networkmodules; and instructions to manage transmissions over the home network.20. The computer program product of claim 19, wherein the transmissionscomprise variable sized packets.